(1) Field of the Invention
The present invention relates to conveying systems, particularly conveying systems wherein the direction of motion of the objects being moved undergoes at least a first change, and especially to multi-level conveyors for transferring book blocks between work stations where diverse operations are performed thereon. More specifically, this invention is directed to the movement of relatively fragile articles, for example multielement articles which have been joined by an adhesive which has had insufficient time to set, between work stations located at different levels in a manner which insures that the initially established positional relationship between the elements is not disturbed. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well-suited for use in the delivery of partially completed books, i.e., book blocks, between work stations of a bookbinding machine which implements an adhesive binding process. Delivery or transfer units for such machines are known wherein the work being processed, i.e., a book or book block, is fed to a conveyor belt, which is inclined downwardly in the direction of travel of the work, after being released by the transport grippers of an adhesive-binding apparatus. At the end of the downwardly inclined conveyor belt, the workpieces are fed, via a generally horizontally oriented conveyor belt, to apparatus which performs the next operation thereon. While being transported, the books or book blocks rest on their spines and are laterally supported by a guide channel. In the case where a cover is to be adhesively secured to the book block, the steps of folding the front and back portions against the block are performed with the aid of appropriate guide elements simultaneously with the delivery of the book blocks from the adhesive-binding apparatus to the succeeding work station.
In order for the bookbinding machine to operate at a speed which does not impose a severe economic penalty on the overall bookbinding process, the adhesive will not have had time to fully cure when the workpieces are transferred from the adhesive-binding apparatus to the delivery or transfer unit which receives the workpieces at a first level and discharges the workpieces at a second level. Accordingly, it is of critical importance that the workpieces be handled with extreme care in order to insure, for example, that the initially established registration between a cover and book block is not disturbed. The previously available delivery units have not been capable of operating at an acceptably fast rate while handling the workpieces with the requisite care. This has been particularly true during the transfer of book blocks from a downwardly inclined conveyor onto a succeeding horizontally oriented conveyor. To the contrary, impact between the leading edge of the book block and the horizontal conveyor at the time of transfer, with resultant "crushing", has been a common occurrence. The forgoing has been particularly true in the situation where comparatively thick blocks were being conveyed at high transport speeds. The above-mentioned crushing, occuring during the transfer of the book block from an inclined transport plane into a horizontal movement plane, leads to "tearing" of the adhesive coating, this being a particular problem in the case of blocks which have been bound with a cold adhesive. While the above-described crushing effect could be reduced by imparting a relatively shallow angle to the inclined conveyor, the net result would be a delivery unit which would occupy an unacceptably large amount of factory floor space.
In situations where the book-block has an "unfavorable" format, for example a block which is very wide in relation to its height, the product being transported has an inherent instability and thus an inclination to overturn, particularly when undergoing a change in direction of movement. Accordingly, in such cases it has been common practice to effect an undesirable, from an economic viewpoint, decrease in operational speed of the book binding machine.
In the use of prior-art delivery units for bookbinding machines, additional problems arise in the case where the book blocks being transferred are of the layered type, i.e., comprised of block portions, with a length equivalent to half-pages. The layers or block portions have a tendency to project, i.e., the spine is not planar, and thus the possibility of tearing of the adhesively coated spine is increased. Any such tearing may lead to the displacement of a pair of adjacent book-block portions relative to one another and thus leads to an unacceptable product.